After quantifying natural anti-NMDAR1 autoantibodies in the plasma of 324 age- and sex-matched subjects (163 healthy controls; 161 Alzheimer’s disease (AD) patients), I found that AD patients carrying higher levels of natural anti-NMDAR1 autoantibodies have significantly (p value: 0.003) higher scores of Mini-Mental State Examination (MMSE score: 23.5) than AD patients carrying lower levels of natural anti-NMDAR1 autoantibodies (MMSE score: 21.4). The gene discussed is GRIN1; the disease is early-onset autosomal dominant Alzheimer disease.